Dumbbell



FIG. 1 is a perspective view of a dumbbell of my design;

FIG. 2 is a top plan view thereof, which is a mirror image of the bottom plan view;

FIG. 3 is a front elevational view thereof, which is a mirror image of the rear elevational view; and,

FIG. 4 is a left side elevational view thereof, which is a mirror image of the right side elevational view. 

The ornamental design for the dumbbell, as shown and described. 